The present invention relates to antennas, and more particularly to broadband antennas for use in television broadcasting.
Sometimes in television broadcasting, the output signals for several transmitters (each signal for a different channel) are coupled to the same antenna for reasons of economy, space, windloading, etc. Because of the high power involved, this antenna must have a broadband impedance characteristic to avoid excessive reflected voltages and currents in transmission lines which can cause losses and difficulties in matching. Even if only a single transmitter is coupled to the antenna, a broadband antenna allows the manufacturer to reduce the number of models he must offer, thereby leading to economies of scale in production. Further, the antenna should have minimum windloading in order to reduce the structural requirements, and hence cost, of both the antenna itself and the support mast therefor.
A typical prior art antenna is the "batwing" antenna, so called because the width of its elements increases as distance from the feed point increases. Unfortunately, such a configuration has maximum windloading at the ends of the elements resulting in a relatively large bending moment on the support mast and the inner (nearest the feed point) ends of the elements, which is where the element widths are narrowest, and therefore least able to resist the bending moment. Further, the batwing antenna may not have a sufficiently broadband impedance characteristic either to allow several transmitters of different channels to be coupled to it, or, to sufficiently reduce the number of models that must be offered.
It is therefore desirable to provide an antenna that has a broadband impedance characteristic as well as minimum windloading.